1. Field of the Invention
This invention relates to transparent permanently miscible, i.e., compatibilized, resin blends containing diene-nitrile copolymer as an impact modifying resin for brittle, hydrolyzed ethylene-vinyl acetate (HEVA) resin containing at least about 40 weight percent interpolymerized vinyl alcohol and no more than about 10 weight percent interpolymerized vinyl acetate.
2. Description of the Prior Art
Hydrolyzed ethylene-vinyl acetate resins containing in interpolymerized form from about 2 to about 60 weight percent ethylene, from about 98 to about 40 weight percent vinyl alcohol and no more than about 10 weight percent of vinyl acetate provide moldings which exhibit excellent oil-resistance, stiffness, hardness, tensile strength, flexural strength, compression strength, abrasion resistance and anti-static charge. Unfortunately, however, these resins possess such a low level of impact-resistance that they are for the most part excluded from engineering applications where high impact strength is an indispensable requirement. Thus, for example, brittle, hydrolyzed ethylene-vinyl acetate resins of the foregoing type, due to their poor impact-resistance, are generally unsuitable molding materials for such important commercial applications as electric switch covers, knobs or cabinets, machine parts such as pulleys, rollers, bars, gears, cams or bobbins, and automotive parts subject to dynamic stress loads.
It has been acknowledged by Takida et al. (U.S. Pat. No. 3,887,649) that past attempts to remedy the low impact-resistance deficiency of hydrolyzed ethylene-vinyl acetate resins by incorporating therein a synthetic rubber such as styrene-butadiene copolymer have not met with success. Thus, while Gardiner et al. (U.S. Pat. No. 3,585,177) and Coates et al. (U.S. Pat. No. 3,549,727) propose the use of nitrile rubbers as impact modifiers for brittle, hydrolyzed ethylene-vinyl acetate resin, experience with these modifiers in simple blends of the hydrolyzed resin has been unfavorable due to the tendency of the blends to separate into the component resins and/or develop an unacceptable degree of opacity.
Acid compatibilized blends of nitrile rubbers and saponified or partly saponified ethylene-vinyl acetate copolymers are disclosed and claimed in my copending application Ser. No. 839,234, filed Oct. 4, 1977 allowed and Belgian Pat. No. 844,744.